The present invention relates to a spraying apparatus and a method of using the same. This spraying apparatus can be used for example in the spraying of the herbicides and insecticides from an aircraft or from the ground. This apparatus provides a means for removing the small drop component of the spray before it leaves the apparatus.
The pesticides used in agriculture and forestry are usually applied in sprays, either aerially or from the ground. A limitation of the atomizers presently available for operational use has to do with the generation and release of small drops, herein defined as measuring drops having diameters less than 100 microns. These drops have slight fallspeeds and are subject to wind drift, causing off-target deposits and potential biological impact outside the treatment areas. Pesticide drift is a significant problem related to the agricultural and silvicultural use of pesticides, and is the basis for several regulatory restrictions on pesticides spraying, and is furthermore the cause of operational inefficiencies.
Various means have been tried to reduce the small drop fraction in pesticide spray clouds. Two operational atomizers have been designed to reduce the small drop fraction of the spray cloud, the Microfoil (Trade-mark of Rhone Poulenc, Lansdale, Pa., U.S.A.) and Thru Valve (Trade-mark of Waldrum Specialties Inc. Ambler, Pa., U.S.A.) booms, but these have achieved only partial success. (Picot et al., 1989, Canadian Journal of Chemical Engineering 67:752-61). Laboratory devices can provide narrow drop size spectra with a very small drop fraction. However, these are not suitable for practical operational applications because of flow rate limitations and the requirement for controlled operating conditions, e.g. lack of mechanical vibrations, constant flow rate, tank mix physical properties etc. (e.g. Merritt and Drinkwater, 1977, Pestic. Sci. 8:457-62).
Polymeric tank mix additives such as Nalcotrol (Trade-mark) have also been developed to reduce the small drop fraction. However, these have not eliminated the small drop fraction but only increased the size of the large drop portion of the cloud (Yates et al., 1985, Report FPM 85-2, USDA-FS, Davis, Calif., U.S.A.). The problem of small drop production is exaggerated when atomizers are mounted on aircraft, because the effect of the aircraft slipstream is to increase small drop proportion due to the relatively large amount of aerodynamic energy available for atomization.
There is an outstanding need for an atomization device for use on aircraft or in ground-based applications that provides better control of the small drop fraction of the spray cloud to substantially reduce or eliminate offtarget deposit.